Lewis on sun 31 aug 03
Feedback as requested: Worked very well indeed. I have a small front-loader
(18" cube internal) and was firing to cone10. I did paint the edges of the
cone with MnO2 and that certainly helped to give a distinctive outline (tho'
what it does to the bending of the cone, I can't say: I meant to put an
untreated cone in as a test and forgot!).
It was quite astonishing how visible everything became - I could even see
the outline of bricks at the back of the kiln. There must be something
going on (someone mentioned a 'lens effect' in the archives), because there
is no way my breath could have cooled the bricks, nor much of the air much
past the spyhole/cones! I wonder, however, how well it would work in a
much more powerful kiln: mine is rated at ant 9.6kw (45A @ 230V), but the
elements are probably rather elderly (temp rise is down to 40degC/hr @ more
than 1220degC); perhaps in a kiln with a much greater heat input, the air
would not be cooled enough or for long enough.
Cone10 was reached, according to my pyrometer at just 1240degC, about 20degC
earlier than I expected (1280degC was grossly overfired). I've just found
the 'computer calculation program' on the Orton website, so I can have that
calculate what Cone10 should be at the temperature gradient my kiln can
sustain, but being Sunday, I don't expect to get the downloaded instructions
for a while. .
Anyway, thanks again to all for input
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